Cockpit door lock
Not wanting to disclose too much about cockpit doors, but rest assured they will unlock by design after a crash.
Just after 9/11 (when the doors were not redesigned yet) deadbolts from the cockpit were used and that would be a post-crash problem.
It is likely that in this case both the cockpit door and the Capt's sliding window (which can be opened from outside) were jammed. Specially because reportedly the pilots were crushed by the "instrument panel behind them" (presumably circuitbreaker panel).